16F88 is not the dream device I thought it was.

[keithdoxey]

Hi All,

When I first saw the features of the 16F88 it seemed like the perfect device to use in my existing project which currently has a 16F628A.

I thought adding the ability for a bootloader would be superb but having examined it more closely I have realised it has a number of shortcomings when used with PBP.

My project currently uses the 628's Comparators and I also use the USART. In addition to that I have an LCD display connected.

Now the problem.....

Microchip in their "wisdom" have seen fit to move the USART to different pins

16F88 = RX on RB2 and TX on RB5
16F628 = RX on RB1 and TX on RB2

initially meaning that the PCB needs to be reworked but more significantly I cant see an easy way to connect an LCD as the USART is split across the lower and upper half of PortB.

I notice that the SSP is also split across the lower and upper half of PortB.

PortA is currently not an option as that port is being used for Analogue.

Is there an easy way of getting an LCD to work?

The only ways I can see for my project are.....

1. Use portA 0-3 for the LCD and use AN4, AN5 or AN6 for the analogue.
2. Use a serial LCD and SEROUT to drive it from a spare pin
3. Use an additonal PIC to create my own Serial LCD.
4. Write my own LCDOUT routine that would allow non-continuous pins to be used.

Non of the above options are particularly appealing.

What on earth made Microchip assign hardware devices to pins spread across a whole port?

Regards

Keith

[tdavis80]

Howdy,

I see that you made this post a month ago. I am not sure if you still are active on this board. I also just started reading about this chip, mainly because of the boot loader capability. I am currently using 16f628a chips with boards (with max232 installed) and thought 'wow, I can simply swap processors'. BUT, moving some of the pins around forces me to not use the 16f88 for now.

Since the 16f88 does not appear to be an exact match up with the 16f628, does it in reality match up with some other older chip?

[keithdoxey]

I see that you made this post a month ago. I am not sure if you still are active on this board.

Since the 16f88 does not appear to be an exact match up with the 16f628, does it in reality match up with some other older chip?

I'm still here. Not posting that much but reading and bookmarking lots of stuff.

During the last week I have got a Keypad multiplexed with an LCD,
got a rotary encoder working,
and have tried out Melanie's 1307 RTC code having modified it to run on an 18F452.

Gradually getting all the building blocks ready for my "big" project.

I still havent used the 16F88 yet as I havent bothered building up a board for it. I was hoping to drop it into my existing PCB's but the different pinouts killed that idea stone dead :(

[Dave]

keithdoxey, I thought I would be on the cutting edge and use the 18F1320 device because of the self program eeprom feature but had many problems with the oscillator circuitry. I fought these problems for months readin g all of the errata sheets. Finally I gave up and went to the 16F88 and to this day have never looked back. The F88 has all the same features as the 1320 except the 4xPLL for the oscillator. I just thought I would add my 2 cents....

Dave Purola,
N8NTA

[keithdoxey]

Finally I gave up and went to the 16F88 and to this day have never looked back.I just thought I would add my 2 cents....


Hi Dave,

I'm sure the 16F88 is a very good device and I will definately be using it in a design that I am working on at the moment. My disappointment was not with the features of the device but the fact that several dedicated hardware pins have shifted places from the 16F628 that I already use meaning that an easy upgrade to a bootloadable device want possible.

If the hardware pins for existing features had been kept compatible with the 16F628 then it would have been just perfect. For new designs it doesnt really matter where the pins are but when you already have PCB's designed and in use then it does become an issue.

Regards

[Dave]

keithdoxey, If the PCB has some complexity to it and you have many already made why not think about a small transition pcb that has a pin header to plug into the exsisting PCB processor socket, and a socket for the new processor? I have done this in the past for upgrades of old PCB rev's during the transition to new artwork. The small pcb wouldn't be much bigger than the exsisting processor.

Dave Purola,
N8NTA